Java Developer Interview Questions & Answers

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Java Developers are computer programmers who are proficient with coding in Java programming language. Their primary responsibilities include designing and implementing java applications, developing and testing software and resolving technical issues that arise.

Whether you're a job seeker preparing to be interviewed for the role of Java Developer or an employer preparing to interview candidates for Java Developer position, these Java Developer interview questions will help you prepare yourself for the job interview session.

Java Developer Interview Questions

Below are a list of some skill-based Java Developer interview questions.

1. Describe your experience working with Java.
2. What kind of certifications do you hold?
3. Why did you choose Java?
4. Show me what you have done with Java
5. Are you currently working on any project?
6. Can you describe a time in your past roles where you implemented a change that led to improvements?
7. What kinds of projects and tasks were you responsible for in your previous role?
8. What data types does Java support?
9. What are constructors in Java?
10. How do you create an object in Java? What is an object used for?
11. What do you consider when choosing between HashSet and TreeSet when you need a set in Java?
12. Can you explain what JVM is?
13. Have you worked with Java frameworks before? If so, which have you selected and why?
14. Can you explain the methods you use to keep your code organized, so it’s easy to work with?
15. Can you describe the key differences between Java and C++?
16. How does the JIT compiler work? What benefits does it offer to programmers?
17. What are Packages and how do they benefit the coding process? Can you provide any examples from your previous experiences?
18. Are you comfortable working in a team environment?
19. What are some of your greatest strengths as a Java developer?
20. What is the most challenging project you’ve worked on in the past?
21. If given the opportunity, what would you improve about the Java programming language?
22. On a scale of 1 to 10, how well do you know the Java programming language?
23. When given a deadline, how do you stay focused on completing your work?
24. Define JAR file and WAR file.
25. What is a final class?
26. Describe your process for debugging code.
27. Which other programming languages do you have experience with?
28. We want to improve the performance of our application. What are some strategies you would use to do so?
29. Describe your experience with enterprise applications.
30. What are JDK, JRE and JVM? Explain each thoroughly.
31. What are some differences between the most popular Java IDEs?
32. Explain your approach when taking on large development projects.
33. Which of the list interfaces is most efficient for adding and removing list elements?
34. What's the basic difference between a List and a Set in Java?
35. When storing sensitive data, would you store the data in a character array or in a string? Why?
36. How and why would you use a Thread Local class?
37. Why can you run Java on any platform? Why doesn't this work in other languages?
38. How would you use a volatile keyword? What's the purpose of it?
39. What do you need to consider when creating an exception in Java?
40. Explain encapsulation.
41. What are the features of an interface?
42. Why would you use a “package” in Java?
43. Explain peerless components.
44. What is a scrollbar?
45. What is a ScrollPane?
46. What is the difference between a heavyweight and lightweight component?
47. What is the difference between an application and an applet?
48. Describe the difference between notify and notifyAll.
49. Why would you make a class private?
50. Define a HashMap.
51. What is object-oriented programming?
52. Explain the definition of an object in OOP.
53. What is a constructor in OOP?
54. What is a default constructor in Java?
55. What is a parametrised constructor in Java?
56. Explain the importance of a default constructor.
57. How can you overload a constructor?
58. Describe the initial value of an instance variable object reference.
59. Explain the difference between methods and constructors in Java.
60. Explain the static variable.
61. Describe the static method and its restrictions.
62. Explain the difference between the static method and the instance method.
63. How do you use the "this" keyword in Java?
64. Describe constructor chaining using the "this" keyword in Java.
65. Explain the Inheritance and its use in Java.
66. What is a superclass, and what is the Java superclass?
67. Define aggregation and its importance in Java.
68. Explain the difference between composition and aggregation in Java.
69. What is the "super" keyword and how is it used in Java?
70. Explain method overloading in Java.
71. How do you identify an exception in Java from another thread?
72. Describe the three types of class loader and why you would use each.
73. When you design an abstract class within Java, why is it important to avoid calling abstract methods inside the constructor?
74. How are method references useful in a Java environment?
75. Can you describe a function that you would only implement using reflection in Java?
76. What is the difference between an input stream and an output stream in Java?
77. Explain the Reader/Writer class hierarchy and the Input/Output stream hierarchy.
78. When would you use BufferedInputStream and BufferedOutputStream?
79. Describe the process of using the FilePermission class in Java.
80. Explain the use of an I/O filter.
81. How do you use the Scanner class to take input in Java?
82. How do you use BufferedReader to take input in Java?
83. How do you use the Console class to take input in Java?
84. Explain garbage collection in Java.
85. How do you use garbage collection for cleanup processing?
86. Can an object be unreferenced? Explain.
87. How do you reference an unreferened object?
88. Explain the Runtime class.
89. What is the relationship between the finalise method and garbage collection?
90. Explain serialisation in Java.
91. Explain deserialisation in Java.
92. Is it possible to prevent child class serialisation in Java? Explain.
93. Explain the differences between serialisable and externalisable interfaces.
94. Explain reflection in Java.
95. How do you use forName() to instantiate the Class class in Java?
96. How do you use getClass() to instantiate the Class class in Java?
97. How do you use .class syntax to instantiate the Class class in Java?
98. Explain the purpose of javap.
99. What does the java.lang.Class class do?
100. What is Java socket programming?
101. Explain the process of connecting two computers using TCP
102. How can you use Java to connect a client and a server?
103. Describe the process for converting an IP address to a hostname.
104. What is threading in Java?
105. What is multithreading in Java?
106. Explain some advantages of multithreading.
107. What is the difference between a thread and a process?
108. What is the difference between a thread class and a runnable interface in Java?
109. Explain whether or not it is possible to start a thread twice.
110. What are daemon threads?
111. Explain synchronisation in Java.
112. What is a deadlock?
113. Explain thread scheduler.
114. Explain the thread pool in Java.
115. How do you reverse a string in Java?
116. Write a Java program for the Fibonacci series.
117. Write a Java program to show scroll up and scroll down.
118. Write a Java program to reverse a string without using string inbuilt function.
119. What makes you stand out from other Java developers?

Java Developer Interview Questions and Answers

Every interview is different and the questions may vary. However, there are lots of general questions that get asked at every interview.

Below are some common questions you'd expect during Java Developer interviews. Click on each question to see how to answer them.

1. Why Do You Want To Leave Your Current Job?
2. What is Your Greatest Strength?
3. Tell Me About Yourself
4. Why Do You Want This Job?
5. Are You a Leader or a Follower?
6. What Is Your Greatest Accomplishment?
7. What is Your Salary Expectation?
8. Do You Have Any Questions for Us?
9. Why Should We Hire You?
10. What is Your Greatest Weakness?

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